Broadband detector bound for Mercury

27 Jun 2006

French firm Sofradir is developing a single detector sensitive over a 1900 nm wavelength range and capable of withstanding the harsh conditions around Mercury.

The European Space Agency (ESA) has selected Sofradir of France to develop and evaluate a single detector capable of imaging in both the visible and infrared. Following this initial feasibility study, the aim is to deploy the detector on ESA's Bepi Colombo mission to the planet Mercury.

"The single detector will be sensitive over the entire wavelength range between 0.4 and 2.3 microns with no spectral gap," Philippe Chorier, space project program manager at Sofradir told Optics.org. "The quantum efficiency will also be constant over the whole spectral range."

The Bepi Colombo mission will use two spacecraft: the Mercury Planetary Orbiter (MPO) that will map the planet's surface at various wavelengths and the Mercury Magnetospheric Orbiter. Sofradir's detector would form part of the visible infrared imaging spectrometer (VN-IMS) housed on the MPO to study the planet's mineralogy.

"The detector being designed is based on Mercury Cadmium Telluride (MCT) made by hybridization of an MCT sensitive array with a silicon read-out circuit," said Chorier. "The detector will have 500 x 256 pixels with a 30 micron pitch. We are adapting an existing Sofradir technology for the needs of the mission."

According to Chorier, one of the most important considerations is producing a detector that can cope with the increased radiation levels experienced around Mercury. "Operating a detector under vacuum in space also requires some specific techniques for the management of thermal exchanges between the detector and the system," he added.

Sofradir will deliver the sample detector in early 2007 and will find out if it has been awarded the contract to develop the detector within the next 12 months. Chorier adds that the technology will be fully available for commercial applications and is not being supplied exclusively to the ESA.

Sofradir products are currently being used on the European military satellite Helios IIa and the Venus Express.